The field of the disclosure relates generally to a diaphragm of a rotary machine, and more particularly to a method and apparatus for replacing a diaphragm of a rotary machine.
At least some known rotary machines, including some known steam turbines, include a diaphragm (or static nozzle) positioned upstream of a row of rotor blades. Such diaphragms include a plurality of airfoil-shaped partitions disposed in a fluid flow path. The partitions are selectively shaped and oriented in a profile that directs the fluid flow at a predetermined angle to the row of rotor blades. For example, the predetermined angle facilitates an efficiency of the row of rotor blades in extracting energy from the fluid flow. However, for at least some known diaphragms, harsh environmental conditions along the flow path, such as, but not limited to, exposure to high-temperature, high-pressure, and/or high-moisture content fluid and/or solid particle impingement, eventually result in creep distortion, erosion, and/or other damage to the partitions, such that the diaphragm requires repair.
At least some known repair methods for such diaphragms include rebuilding each partition using a weld build-up while the diaphragm is in place, and manually grinding the weld build-up to restore the original partition profile. However, in at least some cases, a difficulty in welding and grinding the in-place airfoil results in an inability to restore the original profile, thus changing the predetermined angle and reducing an efficiency of the rotor blades. Alternatively, at least some known repair methods for such diaphragms include welding a pre-machined replacement trailing edge section to an original section of the partition, and hand-machining the weld to restore the original profile. However, in at least some cases, a difficulty in positioning the replacement section with respect to the in-place partition during welding, and a difficulty in machining the in-place partition, again results in an inability to restore the original profile. Moreover, in at least some cases, each such known repair process is time consuming, thus requiring a large amount of out-of-service time for the rotary machine. Furthermore, in at least some cases, each such known repair process results in a diaphragm which again may be susceptible to creep distortion and/or other damage during further operation of the rotary machine, requiring future repairs.